Usage of "much" instead of "many" with countable noun (e.g. Americans)

Question

I found the sentence below in the GMAT exam preparation book:

However much Americans may agree that the financing of elections with special interest money undermines democracy and that campaign finance reform would produce better government, it has been very difficult to push such measure es through a Congress that has been elected using the old financing system.

The book is based on the American English grammar rules. In the book, the author states that this is a grammatically correct sentence.

But why is the noun Americans uncountable in this sentence? Shouldn't it be many Americans instead of much Americans? If the sentence is grammatically correct how the connotation between much Americans and many Americans differs in this case?

---

JFYI, Here is how the whole question looks like. The bolded part should be replaced with a choice from the list below the initial sentence to construct a grammatically correct sentence (the initial sentence may be also correct).

However much Americans may agree that the financing of elections with special interest money undermines democracy and that campaign finance reform would produce better government, it has been very difficult to push such measures through a Congress that has been elected using the old financing system.

1. However much Americans may agree that
2. Despite agreement among Americans to the fact
3. Although Americans agree
4. Even though Americans may agree
5. There is agreement among Americans that

Answer 1

When you see the adverb of quantity doesn't seem to match the associated noun, it could be that it's actually associated with a different (sometimes unwritten) noun. In this case "much" doesn't refer to the number of Americans, but instead the "quantity" of their agreement. A similar example:

However much you agree with me, you should still remember I could be wrong.

The given sentence is fine as it stands, but answer choices #3 and #4 both have a very similar meaning. So this GMAT question is one where you have to play the "standardized test game" and pick the answer that best matches the original, even if multiple choices could be correct.